[Microbit-Python] Battery connector and battery holder

[Damien George]

The KL26Z has a special built-in USB voltage regulator that takes USB VBUS
in and produces 3.3v out.

But yes, it depends on how this is connected internally.  Jonny will need
to tell us what the min/max input is for the battery connector, but I'd say
that 3v, 2x AA batteries, is a very safe bet :)

On Fri, Dec 11, 2015 at 10:38 PM, David Whale <david at thinkingbinaries.com>
wrote:

> I recall that there is a regulator on board on one of the ARM chips. I'm
> not sure what that regulator is specified to, but USB in particular powers
> from 5V, so I doubt the upper limit is specified as 3.6V. I have a
> recollection that powering from the 3V pad misses one diode drop so might
> have different maximum voltage ratings to elsewhere in the circuit.
>
> As the schematics are not in the public domain yet, unless we can get
> Jonny from ARM to confirm minimum/maximum voltage ratings, the best we can
> do is infer these from the data sheets from standard parts, and any
> experimental evidence. I have a recollection that Michael Sparks has had it
> running safely for ages from a higher voltage, which suggests that the
> on-chip regulator is actually a wider voltage range than you suggest.
>
> Wikipedia for example suggests that USB max voltage is 5.25V, so there
> must be some on board regulation to bring this down to the maximum voltage
> of the various cores on the board.
>
> Signal5 V DC <https://en.wikipedia.org/wiki/Direct_current>Max. voltage
>
>    - 5.00±0.25 V (pre-3.0)
>    - 5.00+0.25
>    −0.55 V (USB 3.0)
>    - 20.00 V (USB-PD)
>
>
>
> https://en.wikipedia.org/wiki/USB
>
> I'm wondering if we could get some specific advice from Jonny at ARM here,
> to stop us guessing at this stuff? It's only two numbers (min voltage and
> max voltage), but they would be really useful to know definitively.
>
> David
>
>
> ___________________________________________________________
> David Whale, B.Sc (Hons), MIET
> *Software Engineer and IET Schools Liaison Officer, Essex*
>
> email:  dwhale at theiet.org
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> blog:  blog.whaleygeek.co.uk
>
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>
> On 11 December 2015 at 21:40, Damien George <damien.p.george at gmail.com>
> wrote:
>
>> Hi Tom,
>>
>> I hope this reply is not too late!  I looked at the options for the
>> battery pack and the one with 2x AA would be perfect:
>>
>> https://www.kitronik.co.uk/2268-2x-aa-battery-box-with-switch-and-connector.html
>> .  That would give you about 3v for the microbit which is what it
>> needs.  It can run from between 1.8v and 3.6v, so you definitely don't
>> want more than 2x AA's.
>>
>> Cheers,
>> Damien.
>>
>>
>> On Sun, Dec 6, 2015 at 1:09 AM, Tom Viner <tom at viner.tv> wrote:
>> > Hi all,
>> >
>> > I've found the edge connector breakout board and the motor driver board
>> but
>> > I'm not sure exactly which to buy as a battery pack.
>> >
>> > Something that can run for a while would be good, but blowing up the
>> board
>> > (as happened to poor Mahiri) should be avoided!
>> >
>> > If one of these does the job, I can order my boards and battery
>> connector in
>> > one go from Kitronik.
>> >
>> > Incidentally Kitronik have a load of great micro:bit resources on their
>> > site.
>> >
>> > Cheers,
>> > Tom
>> >
>> >
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>> >
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